stratigraphy of Seymour Four profiles were measured on in areas of little tectonic disturbance, previously selected by photoin- Island, East Antarctic Peninsula terpretation (figure 1). A total of 250 samples were sys- tematically collected within these profiles at approximately 10- meter intervals. Good weather and invaluable support from the

CARLOS MACELLARI and BRIAN T. HUBER helicopter pilots and the crew of the USCGC Glacier made it possible to visit and measure profiles on Snow Hill, Vega, and Institute of Polar Studies James Ross Islands in addition to the planned activities on Ohio State University Seymour Island. We hope these observations and samples will Columbus, Ohio 43210 provide valuable information regarding the correlation of dif- ferent Cretaceous outcrops within the James Ross Island area. They may be particularly helpful in establishing a detailed cor- relation between the Seymour and Snow Hill Island sequences. The Cretaceous stratigraphy of Seymour Island (Isla Vice- The oldest unit exposed on the island is the Lopez de Ber- comodoro Marambio in Argentine literature) has been de- todano Formation of Campanian (Howarth 1966; Olivero 1981) to scribed by Andersson (1906) and more recently by several possibly Maestrichtian (Spath 1953) age (figure 2). The max- authors (Elliot et al. 1975, Rinaldi 1982, and Rinaldi et al. 1972, imum measured thickness was encountered in profile 1(1,190 among others). However, no detailed sedimentological or strat- meters). Several minor units were recognized on the basis of igraphic account of these sediments has yet been published. As lithology, degree of cementation, and content; many of one of the programs on the Seymour Island Expedition, we these were laterally continuous throughout the island. In gen- undertook a comprehensive survey of the Cretaceous portion of eral, the predominant lithology is composed of monotonous, the island. The objectives of this study were to provide the first gray, friable, sandy siltstones. Sporadic intercalations of cal- detailed sedimentological description and a detailed geologic careous, indurated fine-grained sandstones occur within the map of the Upper Cretaceous section, as well as to collect micro- sandy siltstone units, resulting in a more positive relief. Round- and macropaleontological samples in order to refine the present ed to irregular concretions and concretionary horizons are zonation of the sequence. Correlation with other faunas from found throughout the sequence. With the exception of the the Southern Hemisphere will then be attempted, primarily on lower 300 meters of the section, are extremely abundant the basis of the foraminiferal and molluscan specimens. and very well preserved. Different and laterally persistent mac-

BOOMAN POINT

o I 2KM -1 / FOSSIL BAY Du LOPEZ de BERTODANO BAY

CAPE Teim LAMB b tQ .-... ARSEN I I OVE

PENGUIN MEASURED SECTIONS >>^ BAY RINALDI j 01. SECTION QUATER NARY 1 J .:. Q :. GLACIAL DEPOSITS PENGUIN NT TERTIARY Ji Telmi LAMESETA FM. SOBRAL FM. CRETACEOUS III kb I LOPEZ de BERTODANO FM.

Figure 1. Simplified geologic map of Seymour Island showing location of measured sections (after Rinaldi et al. 1978).

68 ANTARCTIC JOURNAL nized in the field within the unconsolidated strata, where faunal ii N S Iv diversity appeared to be quite low. Preliminary observations 400 indicate that the foraminiferal population is more abundant in the lower three-quarters of the Upper Cretaceous sequence. 200 L _ The Sobral Formation, which may be Maestrichtian to Pal- eocene in age, overlies the Lopez de Bertodano Formation in an 1000 apparently concordant fashion. It consists of up to 265 meters of somewhat coarser and more glauconitic silty sandstone, grad- ing into fine-grained sandstones. Rounded concretions and concretionary horizons are frequent. Some beds are laterally continuous, but generally this formation shows a more pro- LU nounced lateral variation than the previous unit. The base of the Sobral Formation is a laterally continuous, 15-20-meter thick, dark brown, well-laminated to flaser-bedded silty mudstone - E]Sob1 Fm which displays local channels. This moderately resistant bed Lopez de 0M. produces a conspicuous positive break an the topography (fig- Bertodano Fm. ure 3). A continuous, well-cemented, large-scale trough cross- bedded glauconitic sandstone appears at approximately 180 Figure 2. General correlation between sections measured on meters from the base of the Sobral. Above this, the sequence Seymour Island. becomes more sandy, glauconitic, and occasionally yellow- stained, with increasingly abundant concretions and fossil rofaunal assemblages were recognized, including numerous wood. All of these characteristics indicate that this may be an ammonites, bivalves, gastropods, echinoderms, corals, and independent unit lithologically similar to the Cross Valley For- sporadic fossil wood. Large benthic foraminifera were recog- mation (Elliot et al. 1975). Fossils found in the Sobral Formation

Figure 3. Oblique aerial photograph showing the major units recognized in the Cretaceous of Seymour Island, and the unconformable contact Sobral Formation; Ksu = upper unit of the Sobral with the Tertiary : KIb = Lopez de Bertodano Formation; Ks = Formation; TeIm = La Meseta Formation; 0 = undifferentiated Quaternary deposits. (Photograph by W. J. Zinsmeister)

69 1982 REVIEW include bivalves, gastropods, echinoderm spines, and abun- Howarth, M. K. 1966. Ammonites from the Upper Cretaceous of the dant wood. James Ross Island Group. Bulletin of the British Antarctic Survey, 10, This work was supported by National Science Foundation 55-69. grant DPP 80-20096. Olivero, E. G. 1981. Esquema de zonaciOn de ammonites del Cretácico Superior del Grupo de Islas James Ross, Antártida. VIII Congresso Geologico Argentino, San Luis, September 20-27, 1981. Acta, 311, 897-907. Rinaldi, C. A. 1982. The Upper Cretaceous in the James Ross Island References Group. In C. Craddock(Ed.), Antarctic geoscience. Madison: University of Wisconsin Press. Andersson, J. C. 1906. on the geology of Graham Land. Bulletin of the Rinaldi, C. A., Massabie, A., Morelli, J., Rosenman, H. L., and del Geological Institute of the University of Upsala, 7, 19-71. Valle, R. 1978. GeologIa de la Isla Vicecomodoro Marambio. Contribu- Elliot, D. H., Rinaldi, C. A., Zinsmeister, W. J., Trautman, T. A., Bryant, ciones del instituto Antdrtico Argentino, 217, 1-37. W. B., and del Valle, R. 1975. Geological investigations on Seymour Spath, L. F. 1953. The Upper Cretaceous cephalopod fauna of Graham Island, Antarctic Peninsula. Antarctic Journal of the U.S., 10(4),182-186. Land. Falkland Islands Dependencies Survey, Scientific Reports, 3, 1-60.

Palynological investigations of Campanian to lower Oligocene sediments on Seymour Island, Antarctic Peninsula -;

A B ROSEMARY A. ASKIN

Geology Department Colorado School of Mines Golden, Colorado 80401

R. F1\11lY F1I:MIN;

Department of Geological Sciences University of Colorado / Boulder, Colorado 80309

C Palynomorphs have been recovered from all of the first prepa - rations of samples collected during the February-March 1982 expedition to Seymour Island. In all, 363 samples were col- lected, mainly from Seymour Island but also from Snow Hill Island (provided by B. Huber), Cape Lamb on Vega Island, The Naze on northeastern James Ross Island, and Cape Melville on King George Island. The stratigraphy of Seymour Island is summarized by Mac- 1 ellari and Huber (Antarctic Journal, this issue; Campanian to 4. ? , Lopez de Bertodano and Sobral Formations) and E F by Zinsmeister and DeVries (Antarctic Journal, this issue; ? Pal- eocene to lower Oligocene, Seymour Island Group). Apart from cemented resistant sandstone beds and concretions, most of 5Opm the sedimentary sequence on Seymour Island is unconsoli- dated. Fine-grained sediments (mud and silt) are abundant in places particularly in the Sobral Formation. Much of the fine- Photomicrographs of fossil pollen from Seymour Island (bar is grained sediment is carbonaceous and highly suitable for pal- equivalent to 50 micrometers). A, M!crocachryidites antarcticus Cookson; B, Phyllocladidites mawsoniiCookson; C, Nothofagidites ynological sampling. fleming!! (Couper) Potonie; D, Proteacidites parvus Cookson; E, The best continuously exposed section of predominantly Haloragacid!tes harris!! (Couper) Harris; F, Tricolpates sp. A, B, D, fine-grained sediment crops out in the central part of Seymour and E occur in the Sobral Formation and throughout the Seymour Island. This approximately 300-meter-thick section includes the Island Group; C occurs in the Seymour Island Group; and F occurs Sobral Formation and is believed to include the Cretaceous- In the Sobral Formation and the Cross Valley Formation.

70 ANTARCTIC JOURNAL